ADS8284
SLAS628–MARCH 2009................................................................................................................................................................................................... www.ti.com
CS
RD
BYTE
t
su5
BUS 18/16
t
en
t
d3
t
dis
t
en
t
d3
t
dis
Hi−Z
Hi−Z
Hi−Z
Valid
Valid
Valid
DB[17:0]
Figure 6. Detailed Timing for Read Cycles
Multiplexer: The multiplexer has two modes of sequencing namely auto sequencing and manual sequencing.
Multiplexer mode selection and operation is controlled with the AUTO, C1, C2, C3, and MXCLK pins.
Auto sequencing: A logic one level on the AUTO pin selects auto sequencing mode. It is possible to select the
number of channels to be scanned (always starting from channel zero) in auto sequencing mode. Pins C1 and
C2 select the channel count (last channel in the auto sequence).
On every rising edge of MXCLK while C3 is at the logic zero level, the next higher channel (in ascending order)
is selected. Channel selection rolls over to channel zero on the rising edge of MXCLK after channel selection
reaches the channel count (last channel in the auto sequence selected by pins C1and C2).
Any time during the sequence the channel sequence can be reset to channel zero. A rising edge on MXCLK
while C3 is at the logic one level resets channel selection to channel zero.
Table 1. Channel Selection in Auto Mode
CHANNEL COUNT PINS
CLOCK PIN
LAST CHANNEL IN SEQUENCE
CHANNEL SEQUENCE
C3
0
C2
0
C1
0
MXCLK
↑
↑
↑
↑
↑
0
1
2
3
X
0,0,0,0..
0,1,0,1,..
0
0
1
0
1
0
0,1,2,0,1,2,0…
0
1
1
0,1,2,3,0,1,2,3,0…
n → 0 (channel reset to zero)
1
X
X
16
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